Edit number two, weeeeeks later, I thought I’d leave here the exacts instructions that allowed me to do what I wanted (thanks to @ermina for the help !).
I went for two RPIs 3B+, and a CM6206 USB sound card for the sound (those cheap 7.1 you find online).
First, after a few difficulties I decided to use two different RPIs, one for sound, one for the video. The sound was glitchy with the software that worked fine with video, and having two RPIs allowed me to have one next to the video projector and one next to one of the speakers, so less cables travelling around the room.
For the sound one, here are the steps I had to walk (the two RPIs have the latest Raspbian installed on it).
First install mplayer, the software that I found to be the best solution for what I wanted, so :
sudo apt-get install mplayer
Then make the rpi able to run headless, otherwise it won’t boot without a screen connected on the HDMI out, so in a terminal :
cd /boot
sudo nano config.txt
in the editor you add at the end :
hdmi_force_hotplug=1
(save and exit : ctrl x, y, enter)
Then write the script that’ll start the player :
cd /home/pi/Desktop
sudo nano autoplay.sh
the editor opens, you write :
#!/bin/bash
mplayer -loop 0 -ao -alsa:device=hardware=2.0 -softvol -volume 20 -channels 4 myfile.wav
(save and exit)
comments : -loop 0 makes it loop indefinitely, -ao and -alsa:device=hardware2.0 to specify to use the USB sound card (which was listed with this number when I looked for it), -softvol to be able to lower the output by command, and -volume 20 sets it at 20% of max volume (so that it is at desired volume without having to change the knobs on the amps when started by someone else), -channels 4 because it is in quadraphony, “myfile.wav” has of course to be changed by whatever you use, and the file is to be located in /home/pi
Then you make your script executable :
chmod +x autoplay.sh
Then you activate crontab, that’ll allow for the device to launch the script when booting :
crontab -e
here you have to choose an editor, nano is easier (to me), so choice 1, then :
@reboot /home/pi/Desktop/autoplay.sh
(save and exit)
That is it ! You can check running :
sudo reboot now
For the video, it was harder to find the working software (as in not glitching when looping, not showing a glimpse of the terminal between loops, etc etc), but in the end it worked with omxplayer so first :
sudo apt-get install omxplayer
then
cd /home/pi/.config/autostart
sudo nano omxplayer.desktop
in which you write :
[Desktop Entry]
Type=Application
Exec=lxterminal -l -e “omxplayer --loop -local --aspect-mode stretch myvideo.mov > /dev/null”
(save and exit)
That is it, so
sudo reboot now
boom, done. At least it worked for me !
Thank to everybody here for suggesting this solution and helping getting started with configuration !
If anybody is interested the show featuring this installation starts September 30th in Rodez (south of France) in the galerie Sainte Catherine.
A good day to everybody !
